1 files changed, 20 insertions, 58 deletions

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index eac31a6059c0..bfb73e025e02 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -3614,68 +3614,30 @@ static void build_zonelists_in_zone_order(pg_data_t *pgdat, int nr_nodes)
         zonelist->_zonerefs[pos].zone_idx = 0;
 }
 
+#if defined(CONFIG_64BIT)
+/*
+ * Devices that require DMA32/DMA are relatively rare and do not justify a
+ * penalty to every machine in case the specialised case applies. Default
+ * to Node-ordering on 64-bit NUMA machines
+ */
+static int default_zonelist_order(void)
+{
+        return ZONELIST_ORDER_NODE;
+}
+#else
+/*
+ * On 32-bit, the Normal zone needs to be preserved for allocations accessible
+ * by the kernel. If processes running on node 0 deplete the low memory zone
+ * then reclaim will occur more frequency increasing stalls and potentially
+ * be easier to OOM if a large percentage of the zone is under writeback or
+ * dirty. The problem is significantly worse if CONFIG_HIGHPTE is not set.
+ * Hence, default to zone ordering on 32-bit.
+ */
 static int default_zonelist_order(void)
 {
-        int nid, zone_type;
-        unsigned long low_kmem_size, total_size;
-        struct zone *z;
-        int average_size;
-        /*
-         * ZONE_DMA and ZONE_DMA32 can be very small area in the system.
-         * If they are really small and used heavily, the system can fall
-         * into OOM very easily.
-         * This function detect ZONE_DMA/DMA32 size and configures zone order.
-         */
-        /* Is there ZONE_NORMAL ? (ex. ppc has only DMA zone..) */
-        low_kmem_size = 0;
-        total_size = 0;
-        for_each_online_node(nid) {
-                for (zone_type = 0; zone_type < MAX_NR_ZONES; zone_type++) {
-                        z = &NODE_DATA(nid)->node_zones[zone_type];
-                        if (populated_zone(z)) {
-                                if (zone_type < ZONE_NORMAL)
-                                        low_kmem_size += z->managed_pages;
-                                total_size += z->managed_pages;
-                        } else if (zone_type == ZONE_NORMAL) {
-                                /*
-                                 * If any node has only lowmem, then node order
-                                 * is preferred to allow kernel allocations
-                                 * locally; otherwise, they can easily infringe
-                                 * on other nodes when there is an abundance of
-                                 * lowmem available to allocate from.
-                                 */
-                                return ZONELIST_ORDER_NODE;
-                        }
-                }
-        }
-        if (!low_kmem_size ||  /* there are no DMA area. */
-            low_kmem_size > total_size/2) /* DMA/DMA32 is big. */
-                return ZONELIST_ORDER_NODE;
-        /*
-         * look into each node's config.
-         * If there is a node whose DMA/DMA32 memory is very big area on
-         * local memory, NODE_ORDER may be suitable.
-         */
-        average_size = total_size /
-                                (nodes_weight(node_states[N_MEMORY]) + 1);
-        for_each_online_node(nid) {
-                low_kmem_size = 0;
-                total_size = 0;
-                for (zone_type = 0; zone_type < MAX_NR_ZONES; zone_type++) {
-                        z = &NODE_DATA(nid)->node_zones[zone_type];
-                        if (populated_zone(z)) {
-                                if (zone_type < ZONE_NORMAL)
-                                        low_kmem_size += z->present_pages;
-                                total_size += z->present_pages;
-                        }
-                }
-                if (low_kmem_size &&
-                    total_size > average_size && /* ignore small node */
-                    low_kmem_size > total_size * 70/100)
-                        return ZONELIST_ORDER_NODE;
-        }
         return ZONELIST_ORDER_ZONE;
 }
+#endif /* CONFIG_64BIT */
 
 static void set_zonelist_order(void)
 {